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    <meta charset="UTF-8">
    <title>Document</title>
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<script type="text/javascript">
    //求出1 - 1/2 + 1/3 - 1/4 …..1/100的和 var i=1; 
    /* 
             1/1
         -   1/2
             1/3
         -   1/4
             1/5
         -   1/6
    */
    var sum = 0;
    for (var i = 1; i <= 100; i++) {
        if(i % 2 == 0){
            sum -= 1/i;
        }else{
            sum += 1/i;
        }
    }
    console.log(sum);
</script>

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